Environmental pressures and ever-tightening governmental regulations have shifted the flexible slabstock polyurethane foam market away from the use of conventional blowing agents and auxiliary blowing agents (ABA's) such as CFC-11, methylene chloride, 1,1,1-trichlorocthane, and methyl chloroform. Generally, this pressure has forced the polyurethane foam industry towards higher-water based formulations. The physical blowing of such high-water polyurethane foam formulations occurs from the carbon dioxide given off as a result of the reaction of water and isocyanate. This blowing replaces the traditional foam expansion derived from the volatilization of conventional blowing agents.
The shift to these higher-water formulations and away from conventional blowing agents has placed many additional demands on flexible slabstock foam production. First, the use of higher amounts of water typically results in increased foam exotherms leading to increased foam discoloration, scorching problems and potential for fire. Second, an increased urea content is common in higher water systems leading to higher hardness values. Thus, some softer foam grades are not readily attainable using only water as the sole blowing agent. Third, a dramatic decrease in foam quality as evidenced by key physical properties of the foam such as compression sets, tensile strengths, tear strengths, and elongation values are also common in most conventional higher water systems. These higher water systems also typically are more difficult to process than their conventional lower water counterparts.
These and related problems have generated several solutions to overcome the inherent pitfalls of current all-water-blown slabstock foam production technology. One of the primary chemical solutions to have evolved to date is the use of low index formulation technologies, such as described in U.S. Pat. No. 4,950,694 to Hager, which allow for lower exotherms and lower load (hardness or indentation force deflection [IFD]) values relative to conventional index, all-water-based systems. With such low index systems, many high quality, lower load foam grades can be produced without the environmentally harmful conventional and auxiliary blowing agents. However, it is desirable to achieve lower IFD ABA-free foams than can be achieved with these low index technologies, which typically are limited commercially to a minimum 25% IFD value (that is, the load at 25% compression of the foam in lbs. per 50 square inches)of about 19-22 lb. in lower density foam (&lt;1.5 lbs./f.sup.3) and greater than about 22 lb. in higher density (&gt;1.5 lbs./f.sup.3) foam, measured according to ASTM-3574.
On another note, the use of amine based isocyanate dimerization or trimerization catalysts has been known for use in manufacturing rigid polyurethane foams. These catalysts lead to isocyanurate linkages which are highly crosslinked and generate brittle, rigid foam structures. Thus, these catalysts have been used in rigid foams wherein, unlike flexible foam, high degrees of cross-linking are desirable. In particular, U.S. Pat. No. 3,804,782 teaches the general use of 1,3,5-tris-(3-dimethylaminopropyl)-1,3,5-triazine (CAS 15875-13-5) in rigid polyurethane foams. Many rigid foam systems have also included N,N-Dimethyl cyclohexylamine (CAS 98-94-2) as an early stage co-catalyst in catalyst blends intended to produce trimerized isocyanate structures in foams (WO9216574).
Additionally, U.S. Pat. No. 4,101,466 discloses the general use of bis-(3-dimethylaminopropyl) methylamine (CAS 3855-32-1) in polyurethane foams and U.S. Pat. No. 5,173,516 teaches the use of bis-(3-dimethylaminopropyl) methylamine as a processing aid for high resiliency (HR) foam systems. The catalyst N,N-dimethylpiperazine (CAS 106-58-1) (DMP) has been used primarily as a processing aid in polyester foams, though one patent citation (U.S. Pat. No. 3,66 1,808) claims the use of N,N-dimethylpiperazine in a catalyst blend for the purpose of reducing the volatility of the catalyst mixture. Such processing is different from the physical enhancement of foam, e.g., an increase foam softness, because while it may increase the cure rate of the foam, the catalysts have not been known to soften the HR and polyester foams.
Moreover, German Patent No. 4030515 discloses the use of 3-(dimethylamino)-1-propylamine (DMAPA) (CAS 109-55-7) to prepare catalysts useful in rigid polycther polyol foams. This catalyst has also been used to catalyze HR foams according to the teachings of DE2116535.